The present embodiments relate to contact detection, and more particularly to a technique, using wavelet analysis, for sensing proximity (contact and near-contact) between a sensor (for example, a read mechanism such as a slider) and an object (for example, a storage medium in a data storage device).
Mass storage devices are one of many components of modern computers. One type of mass storage device is a disc drive. A typical disc drive includes a head disc assembly (HDA) that has one or more magnetic discs which are rotated by a spindle motor at a substantially constant high speed and accessed by an array of read/write heads which store data on tracks defined on the disc surfaces. Each head is carried by a slider, which is designed to “fly” just over the surface of the rotating disc. Each slider is a part of a head-gimbal assembly (HGA), which also includes a suspension (beam and gimbal strut) for positioning the slider and an interconnect (for example, a flexible circuit) that carries electrical signals between the head and drive electronics. A printed circuit board assembly (PCBA), which includes electronics used to control the operation of the HDA, is typically mounted to the underside of the HDA to complete the disc drive.
As the density of data recorded on magnetic discs continues to increase, it is becoming necessary for the spacing between the head carried by the slider and the disc to decrease to very small distances. Spacings of well below 10 nano-meters (nm) are required in some applications. In disc drive systems having such small slider-disc spacing, the possibility of contact between the slider and the disc is relatively high, due to factors such as slider manufacturing process limitations and limited air-bearing modeling capabilities. A system for detecting such contacts is useful for a number of diagnostic tests, enabling assessments such as component-level flyability and durability, drive-level reliability, and production-level screening to be made, as well as providing input to fly-height calibration and adaptive-fly-control systems that enable dynamic adjustment of flying height in certain disc drive systems.